Endogenous neurotoxin-like protein Ly6H inhibits alpha7 nicotinic acetylcholine receptor currents at the plasma membrane

Abstract

α7 nicotinic acetylcholine receptors (nAChRs) are widely expressed in the central nervous system and regarded as potential therapeutic targets for neurodegenerative conditions, such as Alzheimer's disease and schizophrenia. Yet, despite the assumed pathophysiological importance of the α7 nAChR, molecular physiological characterization remains poorly advanced because α7 nAChR cannot be properly folded and sorted to the plasma membranes in most mammalian cell lines, thus preventing the analyses in heterologous expression system. Recently, ER-resident membrane protein NACHO was discovered as a strong chaperone for the functional expression of α7 nAChR in non-permissive cells. Ly6H, a brain-enriched GPI-anchored neurotoxin-like protein, was reported as a novel modulator regulating intracellular trafficking of α7 nAChR. In this study, we established cell lines that stably and robustly express surface α7 nAChR by introducing α7 nAChR, Ric-3, and NACHO cDNA into HEK293 cells (triple α7 nAChR/RIC-3/NACHo cells; TARO cells), and re-evaluated the function of Ly6H. We report here that Ly6H binds with α7 nAChRs on the cell membrane and modulates the channel activity without affecting intracellular trafficking of α7 nAChR. Neuronal nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated cation channels composed of combinations of eight α (α2-7, α9, α10) and three β (β2-4) subunits 1,2. Among those, heteromeric α4β2 and homomeric α7 nAChR subtypes are the two major types abundantly expressed in the central nervous system 3. High expression levels of α7 nAChR in the hippocampus, cerebral cortex, and several subcortical limbic regions suggest its contribution to higher brain functions, such as cognition, attention, memory, and sensory-gating 2 , while impaired α7 nAChR signalling has been implicated in cognitive deficits associated with Alzheimer's disease and schizophrenia 1,4,5. In addition, the expression of α7 nAChRs has been detected in various non-neuronal cells, including immune cells, where it plays a role in immunity and inflammation 6,7. Thus, α7 nAChR modulation has emerged as a novel therapeutic strategy for several neurologic and inflammatory disorders 4,5. α7 nAChRs retain several crucial characteristics that make the subtype peculiar, such as faster desensitisation kinetics and higher Ca 2+ permeability compared to other nAChRs 8,9. In addition, α7 nAChRs can be activated by choline, and are blocked by α-bungarotoxin (α-Bgtx) and methyllycaconitine (MLA), whereas α4β2 nAChRs are insensitive to choline, and are not affected by α-Bgtx and MLA 10-12. In addition to fast desensitization kinetics, α7 nAChRs are neither properly oligomerised nor functionally activated in most cell lines, except a few neuronal or neuroendocrine cell lines after transfection with α7 nAChR cDNA 13-16. To overcome these limitations, α7 and glycine chimeric receptor (α7-GlyR) was designed and used to study the ligand-binding domain of α7 nAChR 17,18. It is well known that in most non-permissive cells, the efficiencies in foldi...

Xanomeline restores endogenous nicotinic acetylcholine receptor signaling in mouse prefrontal cortex

“…The atropine-sensitivity and postsynaptic PKC-dependence of its nicotinic receptor upregulation points to an excitatory muscarinic mechanism, but xanomeline has also been shown to inhibit M4 receptors [100,101] and could potentially disinhibit glutamate release. Our data implicate the involvement of PKC, typically activated by Gα q -signaling, but this signaling also triggers activation of PLC [102] and may regulate GPIanchored lynx family proteins [103] that also modulate nicotinic receptors [104,105] directly [106][107][108] or indirectly [107,109]. We find an improvement in apparent nicotinic receptor availability, however, the question of the density and localization of nicotinic receptors prior toand after treatment remains outstanding.…”

“…The atropine-sensitivity and PKC-dependence of its nicotinic receptor upregulation points to an excitatory muscarinic mechanism, but xanomeline has also been shown to inhibit M4 receptors [98,99] and could potentially disinhibit glutamate release. Our data implicate the involvement of PKC, typically activated by Gα q -signaling, but this signaling also triggers activation of PLC [100] and may regulate GPI-anchored lynx family proteins [101] that also modulate nicotinic receptors [102,103] directly [104–106] or indirectly [105,107]. While the complex action of pharmacological intervention explored here warrants further investigation, our results demonstrate, for the first time, that muscarinic signaling can be harnessed to restore deficits in postsynaptic nicotinic receptors.…”

Gut microbiota composition in colorectal cancer patients is genetically regulated

“…It is associated with IL-1 receptor (IL-1R1), which participates in CRC-associated inflammation and tumor progression 42 . LY6H (lymphocyte antigen 6 family member H) is a pro-inflammatory regulator that inhibits the nicotinic acetylcholine receptor 43 , which is a negative regulator of innate immunity antimicrobial peptides (AMPs) 44 . AMPs are potent pro-inflammatory molecules with a broad antibacterial spectrum, central to the innate epithelial immune response, and their expression can be regulated by the microbiota itself 45 , 46 .…”

Gut microbiota composition in colorectal cancer patients is genetically regulated

“…family member H) is a pro-inflammatory regulator that inhibits the nicotinic acetylcholine receptor [43], which is a negative regulator of innate immunity antimicrobial peptides expresses a tumor suppressor from the p53 family and an important regulator of cell differentiation, proliferation and survival [60]. It also enhances CXCR4 expression [61],…”